We know Mars was once a much more Earth like planet than it is today, with oceans, a weather producing atmosphere, and maybe even life. What caused Mars to lose its atmosphere was not fully understood until recently. As Ethan Siegel explains, data from the Mars MAVEN orbiter has proven Mars lost its atmosphere because its magnetic field collapsed allowing the solar wind to slowly strip away its atmosphere. This changed the planet from the warm and wet place it once was to the cold, dry and apparently lifeless planet we see today.
The discovery suggests a solution that may restore much of Mars’ atmosphere, allowing for oceans to form in just a few decades time. According to a brief study, published at the Planetary Science Vision Workshop 2050, the solution is to place a satellite in the Mars L1 Lagrange point (where the effects of Mars gravity and the Sun’s gravity are in equilibrium) to generate a large magnetic field. The field would act like an umbrella directing the solar wind around the planet as depicted below.
With the solar wind no longer stripping the Mars atmosphere away the geologic processes still creating atmosphere would begin to increase the atmospheric density of the planet, gradually warming it. Once the average planetary temperature increased 4 degrees Centigrade (about 7 degrees Fahrenheit) the process would greatly accelerate as the dry ice caps melt, releasing large amounts of CO2 into the atmosphere. Frozen water still trapped on the planet would melt forming shallow oceans.
While not exactly a perfect place for people, the planet would become much more hospitable for habitation by people.